1. Field of the Invention
The present invention relates to a conversion circuit for a DC brushless motor, and more particularly to a power supply conversion circuit that converts alternating current into direct current for the DC brushless motor.
2. Description of the Related Art
Demands for an AC motor are currently not only to reduce dimensions but also to increase heat dissipation effect. A rotor and a stator construct a traditional AC motor, and the stator alternatively generates a magnetic field to induce the rotor to rotate. A drawback of the traditional AC motor is that the entire structure of the stator coil and the ole plate has been designed with enlarged dimensions to meet requirements of applied in AC 220V or 110V. As a result, decrease of the dimensions of the AC motor has been limited. In miniature fan applications, dimensional limitations of the fan blades and airflow channels are also limited, and thus it is hard in design to increase amounts of air cooling.
As to a traditional DC brushless motor, it has simplified structure that is suitable for a smaller dimension of the miniature fan. This DC brushless motor can be designed not only for an increased amount of air-cooling but also for a decreasingly overall cost of the motor.
FIG. 1 illustrates a schematic view of a traditional driver circuit for a double phase DC brushless motor.
Referring to FIG. 1, the driver circuit for the double phase DC brushless motor includes a first coil L1, a second coil L2, a first transistor Q1, a second transistor Q2, five resistors R1 through R5, a Hall element IC1, a driver element IC2, and a capacitor C. The Hall element IC1 is used for detecting changes of a permanent magnetic field of a rotor to thereby output weaker Hall voltage. And then the Hall voltage is magnified by the driver element IC2 to further output alternative signals (square waveforms) from two terminals O1 and O2 to the transistors Q1 and Q2 respectively. The transistors Q1 and Q2 are actuated in turn to change directions of coil current so as to rotate the rotor.
FIG. 2 illustrates a schematic view of a traditional driver circuit for a single phase DC brushless motor.
Referring to FIG. 2, the driver circuit for the single phase DC brushless motor includes a coil L1, four transistors Q1 through Q4, five resistors R1 through R5, a Hall element IC1, a driver element IC2, and a capacitor C. The Hall element IC1 is used for detecting changes of a permanent magnetic field of a rotor to thereby output weaker Hall voltage. And then the Hall voltage is magnified by the driver circuit IC2 to further output alternative signals (square waveforms) from two terminals O1 and O2 to the bridging transistors Q1 through Q4. The transistors Q1 through Q4 are actuated in turn to change directions of coil current so as to rotate the rotor.
Although both of the above-mentioned single and double phase DC brushless motors have the advantage of reduced dimensions, simplified structure, and lowered overall cost, they are applied only in lower voltage and limited by operating voltage range. In other words, the traditional DC brushless motor is unavailable for the higher voltage of an AC power supply. However, the DC brushless motor is capable of applying the higher voltage of an AC power supply if the driver circuit is improved. Thus, the motor is not only capable of application to a broadened operating voltage range but also accomplishing reduced dimensions, simplified structure, and lowered overall cost.
The present invention intends to provide a conversion circuit converting alternating current into direct current for the DC brushless motor in such a way to mitigate and overcome the above problem.
The primary objective of this invention is to provide a conversion circuit for a DC brushless motor converting alternating current into direct current for the DC brushless motor so that the operating voltage range of the motor is broadened.
The secondary objective of this invention is to provide a conversion circuit for a DC brushless motor comprising a rectifier circuit, a power smoothing circuit, and a low-voltage stabilizing circuit used for providing direct current to a driver circuit of the motor in order to operate it steady.
The present invention is a conversion circuit for a DC brushless motor. The conversion circuit mainly comprises a rectifier circuit, a power smoothing circuit, and a low-voltage stabilizing circuit. The conversion circuit is used for converting alternating current into direct current for a driver circuit of the motor.